Carrier-based pulse-width modulation techniques for asymmetrical six-phase open-end winding drives

The study discusses development, implementation and performance of carrier-based pulse-width modulation (PWM) techniques for an asymmetrical six-phase open-end winding drive supplied by two two-level six-phase voltage source inverters (VSIs). The VSIs are fed from two equal and mutually isolated dc voltage sources, so that the same performance as with a three-level VSI in single-sided supply mode can be achieved. The considered modulation techniques are the in-phase disposition (PD-PWM) and the alternate phase opposition disposition, which are both classified as level-shifted PWM methods, and the phase-shifted PWM method. The performance is studied and compared using computer simulations and experiments undertaken on a laboratory prototype. It is shown that, in contrast to the three-phase and five-phase cases, the PD-PWM method does not offer the best performance.